Incremental build with GCC and manual makefile?

Question

I am coding to the NRF51822 bluetooth chip, in Eclipse with GCC and a makefile that I maintain myself.

My problem is that every time I press build, it will compile everything, which is beginning to take quite some time. I am not that experienced in creating and maintaining make-files, so I have no idea where to start in order to get it to build incremtal instead?

My makefile is composed like this (I know there's a lot, and I haven't created this myself - found it in a tutorial, so I don't know what's relevant and what's not :-) ):

PROJECT_NAME := my_project

export OUTPUT_FILENAME
#MAKEFILE_NAME := $(CURDIR)/$(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
MAKEFILE_NAME := $(MAKEFILE_LIST)
MAKEFILE_DIR := $(dir $(MAKEFILE_NAME) ) 

TEMPLATE_PATH = nrf51_sdk/toolchain/gcc
ifeq ($(OS),Windows_NT)
include $(TEMPLATE_PATH)/Makefile.windows
else
include $(TEMPLATE_PATH)/Makefile.posix
endif

MK := mkdir
RM := rm -rf

#echo suspend
ifeq ("$(VERBOSE)","1")
NO_ECHO := 
else
NO_ECHO := @
endif

# Toolchain commands
CC              := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-gcc"
AS              := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-as"
AR              := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-ar" -r
LD              := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-ld"
NM              := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-nm"
OBJDUMP         := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-objdump"
OBJCOPY         := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-objcopy"
SIZE            := "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-size"

#function for removing duplicates in a list
remduplicates = $(strip $(if $1,$(firstword $1) $(call remduplicates,$(filter-out $(firstword $1),$1))))

#source common to all targets
C_SOURCE_FILES += \
main.c \
file1.c \
file2.c \
file3.c \
file4.c \

#assembly files common to all targets
ASM_SOURCE_FILES  = nrf51_sdk/toolchain/gcc/gcc_startup_nrf51.s

#includes common to all targets
INC_PATHS  = -I Dir1/
INC_PATHS  = -I Dir2
INC_PATHS += -I Dir3
INC_PATHS += -I Dir4

OBJECT_DIRECTORY = _build
LISTING_DIRECTORY =$(OBJECT_DIRECTORY)
OUTPUT_BINARY_DIRECTORY =$(OBJECT_DIRECTORY)

# Sorting removes duplicates
BUILD_DIRECTORIES := $(sort $(OBJECT_DIRECTORY) $(OUTPUT_BINARY_DIRECTORY) $(LISTING_DIRECTORY) )

#flags common to all targets
CFLAGS  = -DSOFTDEVICE_PRESENT
CFLAGS += -DNRF51
CFLAGS += -DS110
CFLAGS += -DBOARD_PCA10028
CFLAGS += -DBLE_STACK_SUPPORT_REQD
CFLAGS += -mcpu=cortex-m0
CFLAGS += -mthumb -mabi=aapcs --std=gnu99
CFLAGS += -Wall -O0 -g3
CFLAGS += -mfloat-abi=soft
# keep every function in separate section. This will allow linker to dump unused functions
CFLAGS += -ffunction-sections -fdata-sections -fno-strict-aliasing
#CFLAGS += -flto -fno-builtin

# keep every function in separate section. This will allow linker to dump unused functions
LDFLAGS += -Xlinker -Map=$(LISTING_DIRECTORY)/$(OUTPUT_FILENAME).map
LDFLAGS += -mthumb -mabi=aapcs -L $(TEMPLATE_PATH) -T$(LINKER_SCRIPT)
LDFLAGS += -mcpu=cortex-m0
# let linker to dump unused sections
LDFLAGS += -Wl,--gc-sections
# use newlib in nano version
LDFLAGS += --specs=nano.specs -lc -lnosys

# Assembler flags
ASMFLAGS += -x assembler-with-cpp
ASMFLAGS += -DSOFTDEVICE_PRESENT
ASMFLAGS += -DNRF51
ASMFLAGS += -DS110
ASMFLAGS += -DBOARD_PCA10028
ASMFLAGS += -DBLE_STACK_SUPPORT_REQD
#default target - first one defined
default: clean nrf51422_xxac_s110

#building all targets
all: clean
    $(NO_ECHO)$(MAKE) -f $(MAKEFILE_NAME) -C $(MAKEFILE_DIR) -e cleanobj
    $(NO_ECHO)$(MAKE) -f $(MAKEFILE_NAME) -C $(MAKEFILE_DIR) -e nrf51422_xxac_s110 

#target for printing all targets
help:
    @echo following targets are available:
    @echo   nrf51422_xxac_s110
    @echo   flash_softdevice


C_SOURCE_FILE_NAMES = $(notdir $(C_SOURCE_FILES))
C_PATHS = $(call remduplicates, $(dir $(C_SOURCE_FILES) ) )
C_OBJECTS = $(addprefix $(OBJECT_DIRECTORY)/, $(C_SOURCE_FILE_NAMES:.c=.o) )

ASM_SOURCE_FILE_NAMES = $(notdir $(ASM_SOURCE_FILES))
ASM_PATHS = $(call remduplicates, $(dir $(ASM_SOURCE_FILES) ))
ASM_OBJECTS = $(addprefix $(OBJECT_DIRECTORY)/, $(ASM_SOURCE_FILE_NAMES:.s=.o) )

vpath %.c $(C_PATHS)
vpath %.s $(ASM_PATHS)

OBJECTS = $(C_OBJECTS) $(ASM_OBJECTS)

nrf51422_xxac_s110: OUTPUT_FILENAME := nrf51422_xxac_s110
nrf51422_xxac_s110: LINKER_SCRIPT=ble_app_hrs_gcc_nrf51.ld
nrf51422_xxac_s110: $(BUILD_DIRECTORIES) $(OBJECTS)
    @echo Linking target: $(OUTPUT_FILENAME).out
    $(NO_ECHO)$(CC) $(LDFLAGS) $(OBJECTS) $(LIBS) -o $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out
    $(NO_ECHO)$(MAKE) -f $(MAKEFILE_NAME) -C $(MAKEFILE_DIR) -e finalize

## Create build directories
$(BUILD_DIRECTORIES):
    echo $(MAKEFILE_NAME)
    $(MK) $@

# Create objects from C SRC files
$(OBJECT_DIRECTORY)/%.o: %.c
    @echo Compiling file: $(notdir $<)
    @echo arm-none-eabi-gcc $(CFLAGS) $(INC_PATHS) -c -o $@ $<
    $(NO_ECHO)$(CC) $(CFLAGS) $(INC_PATHS) -c -o $@ $<

# Assemble files
$(OBJECT_DIRECTORY)/%.o: %.s
    @echo Compiling file: $(notdir $<)
    $(NO_ECHO)$(CC) $(ASMFLAGS) $(INC_PATHS) -c -o $@ $<


# Link
$(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out: $(BUILD_DIRECTORIES) $(OBJECTS)
    @echo Linking target: $(OUTPUT_FILENAME).out
    $(NO_ECHO)$(CC) $(LDFLAGS) $(OBJECTS) $(LIBS) -o $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out


## Create binary .bin file from the .out file
$(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).bin: $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out
    @echo Preparing: $(OUTPUT_FILENAME).bin
    $(NO_ECHO)$(OBJCOPY) -O binary $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).bin

## Create binary .hex file from the .out file
$(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).hex: $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out
    @echo Preparing: $(OUTPUT_FILENAME).hex
    $(NO_ECHO)$(OBJCOPY) -O ihex $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).hex

finalize: genbin genhex echosize

genbin:
    @echo Preparing: $(OUTPUT_FILENAME).bin
    $(NO_ECHO)$(OBJCOPY) -O binary $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).bin

## Create binary .hex file from the .out file
genhex: 
    @echo Preparing: $(OUTPUT_FILENAME).hex
    $(NO_ECHO)$(OBJCOPY) -O ihex $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).hex

echosize:
    -@echo ""
    $(NO_ECHO)$(SIZE) $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out
    -@echo ""

clean:
    $(RM) $(BUILD_DIRECTORIES)

cleanobj:
    $(RM) $(BUILD_DIRECTORIES)/*.o

flash: $(MAKECMDGOALS)
    @echo Flashing: $(OUTPUT_BINARY_DIRECTORY)/$<.hex
    nrfjprog --reset --program $(OUTPUT_BINARY_DIRECTORY)/$<.hex)

## Flash softdevice
flash_softdevice: 
    @echo Flashing: s110_softdevice.hex
    nrfjprog --reset --program nrf51_sdk/softdevice/s110/hex/s110_softdevice.hex

Answer 1

all: clean

check this line. The default (first) Target of your Makefile depends on clean, so before any build is started, the clean target is executed that likely will remove all built files, to rebuild them.

Drop the clean and you should get the incremental behaviour make was designed for.